-LRB- CNN -RRB- -- The electronic component visible in a law enforcement image of an intercepted suspicious shipment from Yemen appears to be a printed circuit board from a disassembled cell phone , an engineer told CNN Friday .

`` This size and the shape of the PCB -LRB- printed circuit board -RRB- are typical to a handset cell phone type device , '' wrote Olivier Clerc , hardware application engineering manager for a large U.S.-based cell phone parts manufacturer .

Clerc prepared the e-mailed analysis of the image at CNN 's request .

His analysis was supported by information from a source close to the investigation into two U.S.-bound suspicious packages , who said the devices appear to be designed to be detonated by a cell phone .

Cell phones have been widely used by terrorist groups as a means of triggering bombs .

`` The component on the top right part of the device seems to be a digital camera sensor , '' Clerc wrote in his analysis . `` The area with a rectangular grey material -LSB- held -RSB- a display that was removed . ''

`` On the left of the device , under the two metallic shield cans are most likely the baseband processor or the display controller . ''

A baseband processor is critical to the function of a digital cell phone .

`` There is as well a coin type cell -LRB- which -RRB- is a backup battery , and 2 Board to board connectors . On one of these connectors is plugged a keypad that was as well removed . Another metallic component on the top left of the electronic board -LRB- partly hidden under a screw -RRB- seems to be a small vibration component , used on cell phones -LRB- when vibrate mode is enabled -RRB- . So this board is very likely to be the main electronic board of a cell phone device . ''

The source close to the investigation said a highly explosive compound known as PETN was found in both devices in amounts large enough to trigger a powerful blast .

PETN was allegedly one of the components of the bomb concealed by Umar Farouk AbdulMutallab , the Nigerian man accused of trying to set off an explosion aboard Northwest Airlines Flight 253 as it approached Detroit , Michigan , on December 25 . AbdulMutallab is alleged to have been carrying 80 grams of PETN in that botched attack .

By comparison , the source said the two devices found in the United Kingdom and the United Arab Emirates on Friday contained multiple times more PETN . Just six grams of the material is enough to blow a hole in the fuselage of an aircraft .

A Google search for the numbered markings on the printed circuit board produced several links to the Bird D736 mobile phone . The D736 is a similar shape to the circuit board . The D736 is a Chinese-brand GSM two-band phone that allows the unit to work in most countries in the world , including the United States .

Clerc cautioned , however , that `` it was not obvious that this board is the D736 phone . ''

In the law enforcement photo , the cell phone circuit board is crudely mounted with screws , metal and plastic fragments to what appears to be a stout metal case . Wires lead from the circuit board out of the frame .

Sources familiar with the investigation tell CNN that the suspicious shipments from Yemen contained computer printers . The metal case on which the circuit board is mounted would be consistent with the frame of a laser printer .

Law enforcement sources have also told CNN that explosives were packed in printer toner cartridges . A U.S. official says while the explosive was likely the highly volatile PETN , testing is ongoing .

CNN 's Pam Benson , John Cunha and Paul Cruickshank contributed to this report .

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NEW : Source : Devices in packages appear to be designed to be detonated by a cell phone

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The electronic device was found in a suspicious package bound for the U.S. from Yemen

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The size and shape of the device are typical to a cell phone , expert says

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Cell phones have been widely used by terrorist groups to trigger bombs